I’ve been that week before more than once. No, the resort pools are not closed; they all have heated pools. That being said, it’s never been warm enough for me to swim there. My kids have a couple of times, but sometimes it gets down in the 30’s at night so is freezing. Daytime can be nice in the 70’s, but also it’s been in the 50’s and we’ve needed jackets and hats.
That is the busiest week of the year at Disney, so prepare for crowds (in normal years, obviously this year is different). It’s lovely, but so busy that you really need to have days planned out well. One trip we did a club level stay, so spent most of our time at the resort enjoying the amenities there.